A. Field of the Invention
The present invention relates to a twin-clutch for an automobile or the like, and in particular to a twin-clutch having two frictional coupling portions and an intermediate plate interposed therebetween.
B. Description of the Background Art
A twin-clutch is generally used for ensuring a large torque transmission capacity within a limited space. In a twin-clutch there are typically two frictional coupling portions and an intermediate plate disposed between a flywheel and a pressure plate, so that a torque is transmitted from the flywheel to a clutch disk assembly through both the frictional coupling portions.
In the above described structure, it is important to control accurately the position and travel characteristics of the intermediate plate interposed between both the frictional coupling portions. For example, the intermediate plate must be kept at an intermediate position between the flywheel and the pressure plate when the clutch is released or disengaged. If the intermediate plate were brought into contact with one of the frictional coupling portions, a drag torque would occur.
Japanese Laid-Open Utility Model Publication No. 1-104436 (1989) discloses a structure developed in view of the above. In this structure, compressible conical coil springs are arranged between a flywheel and an intermediate plate located axially behind the flywheel, and another kind of compressible conical coil springs are also arranged between the intermediate plate and a pressure plate located axially behind the intermediate plate.
According to this structure, both kinds of the compressible conical coil springs act to hold continuously the intermediate plate at a position intermediate between the flywheel and the pressure plate.
In the twin-clutch, however, the intermediate plate is generally coupled to the flywheel by strap plates which extend in the circumferential direction of the disk. The strap plates act as coupling members for transmitting a rotary force of the flywheel to the intermediate plate, and also act as elastic members for axially releasing the intermediate plate from the flywheel. In the twin-clutch disclosed in the above publication, therefore, a load applied by the strap plates and a variation in this load may adversely affect the axial position of the intermediate plate which is to be kept by balanced loads of the two kinds of compressible coil springs. In other words, the position control characteristics for the intermediate plate are affected by both the axial elastic characteristics of the strap plates and the elastic characteristics of both the compressible coil springs, and therefore cannot be determined easily. As a result, the intermediate plate may shift toward the pressure plate or the flywheel from the position intermediate between them when the clutch is disengaged, and thereby the intermediate plate may come into contact with the first or second frictional coupling portion to generate a drag torque.